Means for operating an electron discharge device



MEANS FOR OPERATING AN ELECTRON DISCHARGE DEVICE I H. ROTHE Filed June 25, 1934 INVENTOR HORST ROTHE Patented Oct. 27, 1936 I In UNITED STATES PATENT "oi-"P ca i aosaflza MEANS FOR OPERATING ANELECTRON DISCHARGE DEVICE I Horst Rothe, Berlin, Germany,- assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. IL, Berlin, German a corporation of Germany Application June-=23, 1934, "Serial No. 7sao 29 In Germany June 29, 1933 5. Claims. (chase-+27.)

My invention relates to electron discharge slstance of an element is' Rgin "termsoi ohms, tubes having vindirectly heated cathodes, more and the heating voltage available is 'E in volts, particularly to means for decreasing the initial then the energy developed in the heater body will heating period required to bring the cathodeto; be: i i

5 full emitting temperature. 1 7 v i V E2 In the usual electron discharge tube having-an watts indirectly heated cathode, a heating element'or f" n f heater is provided for heating the electron emit-' Iii accordahce with my'invention the resistor eleting layer or coating on the cathode, and 'isele'cme its a e arra ged so that theY' -y 'b c 10 trically insulated from this layer or coating;v nected in parallel duringthe St i o nitial 1 The emitting layer or coating is heatediromv the heating'period Inasmuch as the efl'ective reheater element either by thermal radiation or 'sistanceoi n-parallel elements each of-R ohms, preferably by'thermal conduction, to the working isequal'to i temperature required for the emission of elecl5 trons. In this latter instance, the cathode supi j l v port consists, for examplaof a tube made from some ceramic material which supports on the 91 fi 8' y th ea in outside upon a suitably prepared metallic inter- I m of Watt? l be equal to H i mediate layer or sleeve, an electron-emissive coating, while the heater element is placed within 1 T; 20

' the ceramic tube. Inasmuch as the ceramic material means an increase-of the mass to beheated, It can seen therefore that Parallel the initial heating period will be increased; in 9 consumption of'power has been other words; the time which it takes the cathode f q h factor q e ce 2 to attain the working temperature after the-heat the 1mm! speriod will thuS'be-reduced to ing current has been switched on is increased fraction-0f 9 original Value- It over the filament type of cathodes. The initial has been foupd b sumcient to make the heat heating time for a given mass of ceramic material er of two reslstor elements which case to be heated in a cathode will be longer the smallfold increase heating energy will he Obtained er the heating power used fo the operation f when the heaters are connectedin parallel.

the cathode. The indirectly heated cathodes of Theflpamllelsonneciion Should be maintained 30 the usual construction require about one minute for l Penod time irequhed to bring h of heating before their full electron emission has "cathode wits WTkihB temperature- In simple been attained, T relatively long heatlng arrangement this change from theparallel conperiod is very undesirable particularly in, broadinecti'oh tonthe serieswmhecuoh the resistor cast receivers. Hence-it is not only desirable elemehtsjcouldbe manually effected by the to decrease the initial heating or starting period ator' u hf h set, though this would where the heating power source is limited, but quire'attehtioh order h t undue overlc'adlhg it is also desirable to diminish the heating or of the cathode would notresultjm the destruc- 40 starting period hi t' been r 'tion of the same. Hence, it is desirable to accom- 40 garded as unavoidable. The arrangement de- "P thechange in t e c rcuitponnectlon autoscribed below is of particular importance inj the ti y FS requislte electron case of cathodes having a heating power of 3 Sion has been b a example. a me rewatt and l lay could" be provided which, after a predeter- The principal object 01', my invention is to prcn length 9 time; Y be determined 5 vide means for decreasing the heating period ren a y nd w ob s-a rule w ld amount quired for bringing an indirectly heat'edcathode Qh Fractions e nd would t of an electron discharge device to full emitting h n e 1n the clrcuIt- HOW V i h n temperature. u device could be also made to depend forits oper- 50 In accordance with my invention, the indirect- M1011 D0 f l S Q current P p ly heated cathode is provided with a'heater c0mby in r n y in the external c ui o a posed of several resistor elements or groups of electrodecarrying direct current, for example, resistor elements. During normal operation the a'node'or the screen grid; The relay could these resistor elements are all'connect'ed in series. be arranged to initiate the change in the con- If the number of elements is n, and it the remotion as soon as the current flowing thru the relay winding has attained a predetermined value. In order to avoid the necessity for using an unduly sensitive type of relay, the relay could also be inserted in a circuit common to several tubes, for example, the anode circuit.

The novel features which I believe to be characteristic of my invention are set forth withparticularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which: Figure l is a diagrammatic representation of a circuit arrangement embodying. my invention. Figures 2 and 3 are diagrammatic representations of modifications of portions of the arrangement shown in Figure 1.

Referring to the drawing, an electron tube II is provided with a plate I I, acontrol electrode II and an indirectly heated cathode It. The cathode heater comprises two resistor heater elements It and it which are provided with three supply leads ll. t1 and it. The heating voltage is furnished from the secondary winding is of a heating transformer 20. The plate circuit which includes the plate voltage supply or source AB, in addition to the output transiormerii, includes electromagnetic means such as a relay having a winding I! and armature It for changing. the connections of the cathode heater elements it and ii. The armature of the relay is mounted on a pivot 21 and is biased by the action of a spring a intothe position shown in the drawing. The armature is provided with two conducting segments II and insulated from each other. The relay winding 1! is suitably by-passed for alternating current by means of condensers II. In the case of rarflo sets operated directly from the supply lines, the relay winding could be replaced by a hlter choke or else the latter could be provided additionally. The segment I! in the position shown in the drawing (which may be regarded as the starting position) and which corresponds to a time at which there is very little or no plate current. closes the contacts a, b. while the segment II closes the contacts c, d. the two resistor elements It and I l under these conditions are connected in parallel across the secondary ll of translormer I. As soon as the plate current has attained a predetermined magnitude. the relay armature It will be attracted by the winding 22 andmoved into the position indicated by the dotted lines, and will be retained in this position as long as the set is in operation. This action opens contacts a, b and c, d, the contact segment It then closing the'contscts e, f to provide a series connection of the resistor elements II and it. As sresuit the consumption of power is reduced to one-fourth of the power consumption during the parallel connection.

The contact constructional the relay may take any number of forms well known in the prior art: for example. they m be of the pot or tank type. I'urthermore, the change in the circuit could be eflected by means of any well known type of time-switch instead of the relay. The time-switch, for example, could be operated by means of a spring motor which could be wound up by manually operated means upon switching on the receiving set. 'lhermostatically operated switch relays, including, for example, a bimetal strip acting as the regulatory means may be used in place of the relay shown, the bimetal strip being responsive to a predetermined temperature of the tube itself or of a series resistance. This series resistance may. ior example. be a salety lamp of miniature size or an ironhydrogen resistor, thru which a current flows, the current being proportional to the cathode temperature.

A thermostatically operated means for actuating the switch arm 24 is shown in Figure 2. The switch arm 24 has connected to it a link II biased to close the series contacts by means of spring 31 and is provided with a catch 33 for engaging latch I connected to the thermostatic element 35 for holding switch 24 in position to make the parallel connections. The thermostatic element is responsive to the heat generated by the heater resistor 30 substituted in. the anode circuit for the electromagnetic coil 22. This resistor element is heated by the current flowing in the anode circuit. When the cathode. has reached its full emitting temperature and normal current flows in the anode circuit thru resistor 36, sufilcient heat is developed to cause the thermostatic element '3! to move to the position indicated in dotted lines to release latch 32 whereby switch Nmoveswith a snap action to change the parallel connection of the cathode heater elements to a series connection.

In the modification shown in Figure 3 a spring motor is depended upon to automatically change the parallel connection of the cathode heaters to a series connection. In this arrangement the latch 34 is provided with a dash pot 31 for willlating the rate of movement of the latch when actuated by means of springs connected to the latch and the switch 30. Upon closing the switch I. the springs as are placed under tension and tend to move the latch 34 away from the catch on the link ii. The dash pot is so regulated that the latch is released when the cathode has reached full emitting temperature, the switch 20 then being moved to its right hand position to open the parallel connection and close the series connection of the cathode heaters. In this last arrangement the electromagnetic coil 2! of the relay may be replaced with the choke I in the anode circuit.

While I-have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim to be new is:-

1. An electron discharge tube having an anode, an indirectly heated cathode, a pair of resistor heating elements for said cathode, circuits for said resistor heating elements, switching means associated with said circuits and movable to one position for connecting the resistor elements in series and movable to another position for connecting said resistor heating elements in parallel. and means responsive to the emission current of said cathode for operating the switch.

2. An electron discharge tube having an indi rectly heated cathode and a plurality of other electrodes, a pair of heater elements for said cathode, circuits for said heater elements, switching means associatedwith said circuits and movable to one position for connecting the heater elements in series and movable to another position for connecting the heater elements in parallel, and means responsive to the current flowing in one of said other electrodes for 0 7 rating said switch. i.

3. An electron discharge tube having an anode and an indirectly heated cathode. a circuit connected to said anode, a pair or heater elements for said cathode, circuits associated with the heater elements, a switch associated with said circuits and movable to one position for connect- :ing the heater elements in series and movable to another position for connecting the heater elements in parallel, and an electromagnetic relay for operating said switch having an actuating winding connected as a choke coil in the'circuit connected to the anode of said electron discharge tube. 1

4. An electron discharge tube having an anode and an indirectly heated cathode, a circuit connected to said anode. a plurality of resistor heatin: elements for said cathode and switching meanstor connecting the resistor elements in series or in parallel, and a iii-metallic strip responsive to the heating action oi the current flowing in the circuit connected to said anode for operating said switch.

5. An electron discharge tube having an anode and an indirectly heated cathode, a circuit connected to said anode, a plurality oi. heater elements for said cathode and switching means for connecting the heater elements in series or in parallel. a resistor in the circuit connected to said anode and a bi-metallic strip responsive to the temperature oi said resistor for actuating said switching means.

- HORST ROTHE. 

